There’s more to say about the latest attempt to deny the mainstream estimate of equilibrium climate sensitivity (e.g. NRC, 1979; Annan and Hargreaves, 2006; Knutti and Hegerl, 2008; Rohling et al., 2012) by Matt Ridley (remember him?) at the Wall Street Journal later. But I just wanted to point out something rather troubling about one of Ridley’s and Nic Lewis’s (the source of Ridley’s claims) citations.

Ridley claimed:

Some of the best recent observationally based research also points to climate sensitivity being about 1.6°C for a doubling of CO2. An impressive study published this year by Magne Aldrin of the Norwegian Computing Center and colleagues gives a most-likely estimate of 1.6°C.

The funny thing about the Aldrin et al. paper is that it really doesn’t find a “low” ECS at all. Their main result is an ECS of 2.0°C, which is completely consistent with the IPCC AR4 range. Moreover, they caution that their main result is incomplete, because it explicitly does not account for the effect of clouds:

When cloud behavior is included as another term, the ECS increases significantly, from ~2.5°C to 3.3°C depending on the values used:

Surely this wasn’t the Aldrin et al. paper Riddley and Lewis were citing as finding an ECS of 1.6°C.

The 1.6°C value literally never appears in the text of the paper.

Of course, it was entirely possible that Aldrin had published another paper on ECS this year finding 1.6°C that I was simply unable to find. I reached out to Bishop Hill and Matt Ridley for some clarification:

I think that some readers, and probably the authors of a paper themselves, might find it at least slightly misleading for you to claim findings on their behalf that the paper itself does not actually state.

The main result from Aldrin et al., as reported by Aldrin et al., is an ECS of 2.0°C. The authors caution that this result probably isn’t an apples to apples comparison to other ECS estimates due to the unaccounted for cloud term, and find that the value increases to ~2.5-3.3°C with clouds.

Rather than report either of these values, you simply claim Aldrin et al. “an impressively thorough study, gives a most likely estimate for ECS of 1.6°C…”.

Ridley likewse claims, “An impressive study published this year by Magne Aldrin of the Norwegian Computing Center and colleagues gives a most-likely estimate of 1.6°C.”

It would be easy for me to lob accusations of bad faith, as we don’t know each other and this is just the internet. Instead, I would encourage you, if your goal is to reach as wide an audience as possible, and try to make an impact beyond the “skeptic” and conservative blogospheres, to be more upfront about the scientific literature about ECS.

Ignoring the two main findings of a paper for values that you’re either estimating from a curve or are creating yourself based on data not used by the paper will be seen by at least some people to be misleading. Claiming that ECS cannot be estimated by paleo data is absurd, especially when so many are aware of efforts like the PALAEOSENS project and various paleoclimatic intercomparison groups.

I won’t attempt to read minds or divine motivations. I will simply suggest that what you have been doing thus far will cause some people to dismiss what you’re trying to say due to perceived dishonesty.

I hope you take this criticism in the constructive context in which it is being offered. There will be plenty of time for name-calling and insults later.

What groundbreaking evidence does Ridley marshal in defense of his rejection of mainstream science?

I was curious. Ridley ostensibly is a cut above the average denizen of WUWT. He was trained as a zoologist before taking up science writing. He has articles frequently published in the mainstream press, as the delicious-in-hindsight tweet by Andy Revkin reflects. He’s widely acclaimed for popularizing science concepts for mainstream reading audiences. So whatever Ridley had must be good, I thought. His arguments would reflect the best of the “skeptics'” best.

It turned out I was wrong. Or perhaps, I was right, and Ridley was bringing the best of the “skeptics'” best. Either way, it was an enormous disappointment. Ridley’s speech turned out to be a textbook Gish Gallop, full of false claims, logical fallacies, and trivially true but irrelevant “facts”. It was, as I put it at Keith Kloor’s blog, “skeptic” bingo.

Sea level rise is small and is decelerating!

Methane isn’t increasing!

Hockey Stick!

Etc.

I don’t think I will do a point by point rebuttal to every claim in Ridely’s speech at this time (maybe later, for sport, time permitting). But suffice it to say that while Ridley is being lauded by the denialosphere now, he’s actually done them a tremendous disservice. With this speech, he’s fully exposing himself as a crank, and has thus reduced the ever-dwindling list of “credible skeptics” one further.

And in case anyone is curious, while the year-to-year variability is significant, on climate-relevant timescales, sea level rise is indeed accelerating (Church and White 2011; Rahmstorf and Vermeer 2011).

But more to the point, absent emissions stabilization, sea level rise is going to increase, reaching 1m or more by end of century (Vermeer and Rahmstorf 2009).

Failure to stabilize emissions will almost assuredly result in the eventual collapse of the Greenland and Antarctic ice sheets, committing the world to multimeter sea level rise that will be for all practical purposes irreversible. Many of Ridley’s claims similarly depend on falsely equivocating between concern over future climate changes absent emissions stabilization (and their relative irreversibility over human timescales) and what is happening at present. This couldn’t be more misleading.

As you might imagine, given the way this is going, Ridley’s claim that methane isn’t increasing is also false. Methane levels today are much higher than they’ve been over at least the past 800,000 years and continue to increase (Loulergue et al., 2008; NOAA AGGI).

The “hockey stick” nonsense has been done to death. And “skeptics” like Ridley inevitably fail to mention the main points: the “hockey stick” has basically nothing to do with either the attribution of recent warming to humans or the seriousness of future warming; the ostensible statistical problems in the original Mann et al. paper were overstated by its critics, and the actual problems it did have don’t tremendously affect its results (Huybers 2005; Wahl and Amman 2007); moreover, independent Northern Hemisphere reconstructions (including “skeptics'” own) show more or less the same results as Mann et al.’s recent work- the warming during the instrumental record exceeds peak Medieval temperatures (Ljunqvist 2010; Loehle and McCulloch 2008; Mann et al., 2008; Moberg, et al., 2005).

People like Ridley spend an awful lot of time listening to “skeptic” bloggers like Jo Nova and Bishop Hill, but seem to have no grasp of basic Earth systems science. And it shows. There is a total lack of coherence in Ridley’s claims. Ridley wants us to know that the climate changed rapidly in the past- but yet we’re also supposed to believe that climate sensitivity is very small. He also flubs basic concepts- equilibrium sensitivity is not the same thing as transient sensitivity (i.e. how much we will warm in response to a given increase in radiative forcing is larger than how much warming we’ll experience in the near term due to things like the thermal inertia of the ocean).

Perhaps Ridley can follow his own advice and “unlearn” the lies, fallacies, and nonsense he’s being cheered for regurgitating. Though let’s just say I’m a little skeptical of the prospect.

References:

Church, J.A., and N.J. White (2011): Sea-Level Rise from the Late 19th to the Early 21st Century. Surveys In Geophysics, 32, 4-5, 585-602, doi:10.1007/s10712-011-9119-1.

Huybers, P. (2005): Comment on “Hockey sticks, principal components, and spurious significance” by S. McIntyre and R. McKitrick. Geophysical Research Letters, 32, L20705, doi:10.1029/2005GL023395.Ljungqvist, F.C. (2010): A new reconstruction of temperature variability in the extra-tropical northern hemisphere during the last two millennia. Geografiska Annaler: Series A, 92, 3, 339-351, doi:10.1111/j.1468-0459.2010.00399.x.